Semaphorins
Semaphorins are a family of membrane bound and secreted proteins classified into eight sub-classes based on their structural domains. Semaphorins mainly regulate focal adhesion assembly/disassembly and induce cytoskeletal remodeling, thus affecting cell shape, cell attachment to the extracellular matrix, cell motility, and cell migration. Although Semaphorins were originally identified as affecting axon guidance during development of the nervous system, they are now thought to fulfill diverse physiological roles including organogenesis, vascularization, angiogenesis, neuronal apoptosis, and neoplastic transformation. Additionally, recent studies pointed to the involvement of Neuropilin-1 (a receptor for semaphorin 3) and certain Semaphorins in the regulation of the immune system, and thus these Semaphorins are denoted “immune Semaphorins”.
The seven class-3 Semaphorins (Semaphorin 3s), designated by the letters A-G, are the only vertebrate secreted Semaphorins. Neuropilins (Nrps) and the type A/D family Plexins (Plexin-A1, -A2, and -A3, and Plexin-D1) act as receptors for Semaphorin 3. Each Semaphorin 3 family member shows distinct binding preference for Nrps. Each Sema3-Nrp complex associates with specific plexins to mediate downstream signaling. Most membrane-bound vertebrate Semaphorins directly bind plexins, while class-3 Semaphorins require Neuropilins as obligate co-receptors.
Semaphorin 3A (hereinafter “Sema3A”), a class-3 secreted member of the Semaphorin family, has been established as an axonal guidance factor during development. Interestingly, several lines of evidence suggest that Sema3A also affects immune cell functions. Sema3A has been shown to be expressed by activated T cells and inhibit T cell proliferation and cytokine secretion (Catalano, A. et al., 2006, Blood 107: 3321-3329; Lepelletier, Y. et al., 2006, Eur. J. Immunol. 36: 1782-1793). Moreover, the expression of Sema3A, Neuropilin 1 (NP-1), Neuropilin 2 (NP-2), and Plexins was found to be increased on differentiating macrophages and on activated T cells (Ji J D et al., 2009, Human Immunol., 70(4): 211-7). In another study, kidney biopsies from lupus glomerulonephritis (LGN) patients showed stronger staining with anti-NP-1, anti-Semaphorin 3A and anti-Semaphorin 4A antibodies as compared with either normal biopsies or biopsies from patients with primary nephropathy and proteinuria (Vadasz Z. et al., 2011, Lupus, 20:1466-1473). A subsequent study has shown that Sema3A serum levels in SLE patients are significantly lower than in healthy individuals (Vadasz Z. et al., 2012, Arthritis Research & Therapy, 14:R146).
Semaphorins in Cancer
Semaphorin 3A was found to be related to several malignancies. In breast cancer semaphorin impedes tumor cell migration and growth (Mishra R. et al., Oncogene 2014, 1-12). Glioblastoma Multiforma, is a malignant type of glioma having a tendency for aggressive local spread. This tumor expresses high level of semaphorin 3A receptor (T. Bagci et al., Oncogene (2009) 28, 3537-3550). Lower expression of semaphorin-3A was detected in Non Small Cell Lung Cancer (NSCLC) tissues following comparison with control non cancerous lung tissues (Zhou H. et al., Oncology Letters 7: 1395-1400, February 2014).
Urothelial Cell Carcinoma
Urothelial Cell Carcinoma (UCC), also known as Transitional Cell Carcinoma (TCC), is a type of cancer that typically occurs in the urinary collecting system (the kidney, ureters, urinary bladder, urethra and accessory organs). It is the most common type of bladder cancer and cancer of the ureter, urethra, renal pelvis and calices and also urachus. It is the second most common type of kidney cancer, but accounts for five to 10 percent of all primary renal malignant tumors and over 90% of bladder tumors. TCC arises from the transitional epithelium, a tissue lining the inner surface of these hollow organs. Patients with non invasive urothelial carcinoma are at a high risk for recurrence and progression, therefore a lifelong follow-up is needed.
Bladder cancer is the fourth most common cancer in the United States. The disease exists in two main forms: non-invasive bladder carcinoma, which lacks invasion into surrounding muscle tissue and is the more common form accounting for 75% of all cases, and muscle invasive bladder carcinoma, in which the tumor spreads through the lining of the bladder and invades the muscular wall of the bladder. Invasive cancer may grow through the bladder wall and spread to nearby organs. The muscle invasive tumors are associated with a high risk of metastases and a poor prognosis.
The gold standard for detecting bladder cancer is cystoscopy (an endoscopy of the urinary bladder in which a fiber optic device is inserted via the urethra). However, this procedure is invasive, uncomfortable, costly and may provoke bleeding, infection, urethral trauma, and urethral stricture. Moreover, cystoscopy may miss certain lesions, in particular small areas of carcinoma in situ. Computed Tomography (CT) scans may also be utilized for diagnosis of bladder cancer but this procedure exposes the patient to an ionizing radiation, and thus may lead to secondary malignancy. CT scans are further associated with intravenous contrast material injection which may cause anaphylactic shock, renal failure and cardio-vascular failure. Urine cytology, which assesses presence of cancerous cells in the urine, is the only noninvasive method used to detect recurrent bladder cancer, however it has a sensitivity of 50% at best.
There remains an unmet need for reliable, and accurate non invasive methods for diagnosing urothelial cancer in a subject and for determining disease staging and prognosis. There is also an unmet need of methods for determining the effectiveness of an anti-cancer therapy of a subject. A sensitive and specific method for disease detection would allow screening population at risk and healthy population. This cannot be done today as cytology sensitivity is low.